1. Field of the Invention
The present invention relates to a ball valve or a plug valve comprising a body defining a housing for a movable member consisting of a ball or a plug, this movable member being provided with a substantially cylindrical channel arranged to be brought into line with the continuation of an inlet conduit or outlet conduit when the valve is open, and in a direction which is substantially perpendicular to the axis of the inlet and outlet conduits when the valve is closed.
2. Discussion of Background
At present, ball valves of the known type are- subjected to considerable seat erosion due to the differential pressures which occur during the valve opening or during the valve closing. Due to these differential pressures, the potential energy is converted into kinetic energy which generates local velocity increase of flow at small opening, which is the primary source of erosion and turbulence. These differential pressures also cause vibrations inside the valve which increase the noise level and mechanical fatigue. As soon as the seals are damaged, the said valve can no longer be said to be tight.
The ball valve described in the French patent application FR-A-2 506 420 attempts to propose a solution to overcome the problems outlined above. With this in mind, the ball comprises two turbulence attenuators located in the areas of turbulence which form when the valve is opened and closed. These turbulence attenuators are comprised of stepped and perforated walls. In practice, this solution is not entirely satisfactory for the following reasons:
The attenuators are located in the ball's sealing area in such a way that the pressure reduction and the conversion of energy affect the seat's performance.
The ball can not be closed at an angle of 0.degree., but at a negative angle, which is proscribed for regulating control servomotors.
The pressure reduction obtained with this valve is insufficient given the size of the attenuators.
Furthermore, the standard valves industry can not make use of this invention as it implies a costly and bulky oversizing of the ball.